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Evidence summaries

Signs, Symptoms, and Simple Tests in the Diagnosis of Myasthenia Gravis

Some symptoms (speech becoming unintelligible after prolonged periods) and signs (peek sign) may be useful to confirm the diagnosis of myasthenia gravis, while the results of some tests (ice test, sleep test, response to anticholinesterase agents) may be useful to rule-in or rule-out the condition. Level of evidence: "C"

A systematic review 1 including 15 studies with a total of 896 subjects (358 myasthenia gravis patients) was abstracted in DARE. All of the included studies were diagnostic case-control studies. The positive LR reported for 'food in mouth after swallowing' was 13.0 (95% CI: 0.85, 212.0) and the negative LR was 0.70 (95% CI: 0.58, 0.84). For 'unintelligible speech after prolonged speaking', the reported positive and negative LRs were 4.5 (95% CI: 1.2 to 17.0) and 0.61 (95% CI: 0.46 to 0.80), respectively. The positive LR reported for the peek sign was 30.0 (95% CI: 3.2, 278.0) and the negative LR was 0.88 (95% CI: 0.76, 1.0). For the sleep test, the reported positive and negative LRs were 53.0 (95% CI: 3.4 to 832.0) and 0.01 (95% CI: 0.00 to 0.16), respectively. The pooled positive and negative LRs for the ice test were 24.0 (95% CI: 8.5 to 67.0) and 0.16 (95% CI: 0.09 to 0.27), and the pooled positive and negative LRs for the anticholinesterase test were 15.0 (95% CI: 7.5 to 31.0) and 0.11 (95% CI: 0.06 to 0.21), respectively.

Explanation of tests and signs: Sleep test: Resolution of ptosis or ophthalmoparesis immediately after a 30-minute period of sleep; the reappearance of the myasthenic signs over the next 30 seconds to 5 minutes adds further confirmation. Ice test: Two or more millimeters of improvement in ptosis after 2 minutes of ice application on the ptotic eyelid is considered a positive ice test result. Peek sign: On lid closure to command, the orbicularis muscle initially may achieve lid apposition; however, as the patient continues to try to keep the eyes forcefully closed over a minute, the orbicularis oculi fatigues, and sometimes the lids separate to show a rim of sclera, with the patient appearing to "peek" at the examiner.

Comment: The quality of evidence is downgraded by limitations in study quality and by indirectness.

    References

    • Scherer K, Bedlack RS, Simel DL. Does this patient have myasthenia gravis? JAMA 2005 Apr 20;293(15):1906-14. [PubMed][DARE]

Primary/Secondary Keywords